1. Field of the Invention
The present invention relates to a microelement picking and releasing device for use to pick up/release micrometer/nanometer elements and, more specifically, to a microelement piezoelectric feedback type picking arrangement, which uses a progressive electrode to achieve uniform and precise deformation, piezoelectric feedback to control clamping force, and an IDT (interdigital transducer) to produce surface acoustic wave and to achieve accurate releasing.
2. Description of the Prior Art
When micrometer/nanometer electronic elements have become more and more popularly used in an electronic device, it is important to control the operation of picking and releasing micrometer/nanometer elements. When the size of micrometer elements below 0.01 mm, the physical interactions between micrometer/nanometer elements, such as surface tension, van der Waal force, surface hydrogen bond reactive force, etc., become important factors in micro/nanometer operation. Various picking-releasing measures have been disclosed. However, the known picking-releasing measures have their limitations because they are not free from the affection of element dimensional factor. The sizes of elements affect picking and releasing operations. The physical interactions between pickup (picking-releasing apparatus) and element make the releasing action difficult. During a releasing operation, it may need to apply an external energy to the pickup, or to control the oscillation of the whole pickup. However, it may damage the element when applying an external energy to the pickup or controlling the oscillation of the pickup. Further, when operating a microelement pickup (picking-releasing apparatus), it is difficult to control the clamping force. In order to control the clamping force, sensor means may be provided for detecting the applied force. However, the installation of such sensor means greatly complicates the circuit design of the pickup and also greatly increases the manufacturing cost.
With respect to operational force, it can be a contact force or non-contact force. A contact force is achieved by means of surface tension, static electricity, or magnetic force. When a non-contract force is used, it needs to apply an added energy during releasing. For example, it needs to heat water drop to the boiling point in order to eliminate surface tension. However, the added energy may damage the micrometer/nanometer element, or cause instability of the system. Furthermore, it is difficult to control the direction of the element when a non-contact force operation method is used. When a contact force method is adopted, the design of driving is commonly achieved by means of a piezoelectric material. By means of controlling electric field to control the amount of deformation of piezoelectric material, the operation of the pickup is controlled. Conventional piezoelectric pickups commonly have a single electrode with a complicated design. These conventional designs have application and precision limitations. When applying added energy or oscillating the pickup during releasing operation, the element may be damaged or not accurately positioned.
The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a microelement piezoelectric feedback type picking and releasing device, which eliminates the drawbacks of the aforesaid prior art designs. A progressive piezoelectric electrode is provided having the electrode area gradually reducing from the fixed end toward the free end. By means of controlling the applied voltage, the progressive piezoelectric electrode causes the pickup to achieve precise deformation and a big amount of displacement. An interdigital transducer is provided near the front end of the pickup to detect the voltage change upon contact of the pick up with the microelement, and to feed back the detected signal for accurate clamping force control. Further, controlling electric current to the interdigital transducer (IDT) to produce surface acoustic wave enables the pickup to conquer the surface physical reactive force of the microelement, enabling the microelement to be released to the assigned position accurately. According to the preferred embodiment of the present invention, the microelement piezoelectric feedback type picking and releasing device comprises a piezoelectric material, an IDT (interdigital transducer) plated and a progressive electrode plated on the piezoelectric material, the progressive electrode having a plurality of electrode elements of different sizes arranged in proper order in one direction, the IDT forming a releasing unit by means of surface acoustic wave/ultrasonic wave and serving as a voltage signal feedback sensor for clamping force control.